1. Field of Invention
The present invention relates to a liquid crystal driving circuit. More particularly, the present invention relates to low power consumption LCD driving circuit.
2. Description of Related Art
How to reduce the power consumption of the electronic device is an important object in the past few years. Such as the cellular phone, there is only a limited space in a cellular phone, a large capacitance battery cannot be mounted, and power consumption of a circuit in the phone needs to be reduced as much as possible to extend the usage time.
FIG. 1 depicts a block diagram showing a conventional signal line driving circuit. The driving circuit includes a shift register 110, a plurality of data latch circuits 120, a load latch circuit 130, a level shifter 140, a D/A converter 150, a plurality of buffer amplifiers 160, and a reference voltage generating circuit 180. The shift register 110 is arranged for successively shifting a shift pulse supplied from the outside in synchronization with a transfer clock. The data latch circuits 120 are arranged for latching digital grayscale data in synchronization with the shift pulse outputted from each output terminal of the shift register 110. The load latch circuit 130 is arranged for latching outputs of the data latch circuits 120 at the same time. The level shifter 140 is used for converting a level of an output of the load latch circuit 130. The D/A converter 150 is used for outputting an analog voltage in accordance with an output of the level shifter 140. The buffer amplifiers 160 are arranged for buffering an output of the D/A converter 150. The reference voltage generating circuit 180 is used for generating an analog reference voltage corresponding to the digital grayscale data. Each output of the buffer amplifiers 160 is supplied to each signal line 170.
Hence, the large number of buffer amplifiers 160 consumes the power of electronic devices, and increases the chip size of the driving circuit. Therefore, it is desirable to improve the design of the liquid crystal driving circuit to reduce the number of buffer amplifiers and the power consumption.